CZ290901B6 - Plant for manufacturing cement clinker - Google Patents

Abstract

The present invention relates to a plant for manufacturing cement clinker. The plant consists of a preheater, a calciner, in which the raw material is calcined at a temperature of more than 800 degC and where fuel and oxygen-containing gas are fed to the lowermost zone of the calciner, and a kiln. The calciner (2) is provided with a fixed bottom (27). A smaller, controlled amount of uncalcined raw meal can be fed to the lowermost zone (23) in the calciner. The invention provides a plant for manufacturing cement, in which it is possible to burn lumpy fuel in a calciner, while simultaneously maintaining the possibility of increasing the time of retention and possibly the temperature of the material being fed to the lowermost zone in the calciner.

Description

Equipment for the production of cement clinker

Technical field

The present invention relates to an apparatus for producing cement clinker. The apparatus consists of a preheater in which the raw materials are preheated, a roasting furnace in which the raw material is calibrated at a temperature of more than 800 ° C, and wherein the oxygen-containing fuel and gas are introduced into the lower zone of the roasting furnace, and raw materials burn and transform into clinker.

BACKGROUND OF THE INVENTION

In a conventional cement clinker plant, up to 20% of the base fuel in a rotary kiln can be replaced with cheap waste fuel such as rubber tires without sacrificing the quality of the final cement product.

Normally a maximum of 40% of the total fuel consumed in a cementing plant is burned in a sintering furnace, with the remaining 60% burned in a roasting furnace. As a result, in a conventional furnace, only about 20% of the 40% of the fuel burned in the rotary kiln, that is, about 8% of the total fuel, can be replaced by waste fuel. Therefore, it would be advantageous if a larger part of the fuel burnt in the roasting furnace could be replaced by waste fuel.

However, there are certain limitations in the types of waste that can advantageously be burned in a roasting furnace.

The temperature in the roasting furnace is typically in the range of 850 to 950 ° C, which means that it is not advantageous to incinerate hazardous waste, since noxious substances that must be decomposed and neutralized during incineration would require higher temperatures and longer retention times than appropriate in the roasting furnace. roast.

The roasting ovens are normally of the pendant type, which means that the preheated air from the clinker cooler or the oven is routed through a conduit and a flexible tube bent to the bottom of the roasting oven. When lump waste, such as torn rubber tires, is fed into the baking furnace, it falls down into the arc of the tube and causes it to jam. As a result, furnaces with a bottom configured in this manner are not suitable for burning lumpy fuels.

It may also be difficult to use fuel that is difficult to ignite, for example certain types of coal with a low content of volatile compounds, since the retention time in the roasting furnace is relatively short and the temperature is relatively low.

Danish Patent No. 155,726 (Metallgesellschafit AG) discloses a fluidized bed roasting furnace in which oxygen-containing fluidizing air is fed through the bottom of the roasting furnace and wherein the oxygen-containing secondary air can be introduced horizontally to an area extending from at least 1 meter above the starting point of fluidizing air to at least 30% of the roasting furnace.

In this system, at least 65% of the fuel that is used to cover the total heat consumption is fed to the roasting furnace, and at least 10% of the fuel is fed to the next furnace. By creating a fluidized bed in a roasting furnace, a high degree of calcination can be achieved, even in the case of variation in grain size. However, fluidization means that a significant amount of false air is introduced into the system, which has an adverse effect on the use of heat. The simultaneous injection of fluidizing air also requires some energy input.

Danish patent DK 170368 (F.L. Smidth & Co. A / S) discloses the practice of introducing lumpy material such as jerky car tires into a decomposition chamber installed in conjunction with a roasting furnace. According to this patent it is preheated or partially

The calcined crude pulp is introduced into the decomposition chamber for heating the waste fuel. The temperature to be reached in the decomposition chamber must be sufficiently high to ensure that the pyrolytic process is carried out, but must not be so high as to result in the granulation of the raw debris. The combustible gases from the decomposition chamber gradually flow into the combustion chamber 5 consisting of the roasting furnace itself and the remaining products are extracted from the bottom of the decomposition chamber and can be transported to the rotary furnace. However, the use of a decomposition chamber in which an air deficiency is used does not allow the extraction of the same amount of energy from the waste in the roasting furnace as can be obtained in conjunction with complete combustion under a sufficient oxygen supply.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a cement making plant in which it is possible to burn lump fuel in a roasting furnace while maintaining the possibility of extending the retention time and possibly raising the temperature of the material introduced into the lower zone in the roasting furnace.

This object is achieved by the roasting furnace having a solid bottom, thereby allowing combustible material introduced into the roasting furnace to settle to the bottom, and by introducing the oxygen-containing gas horizontally into the roasting furnace through openings in the lower zone of the roasting furnace. care. That the oxygen-containing gas is indicated horizontally means that the gas is introduced through the vertical sides / walls of the roasting furnace and not through the bottom.

By introducing combustible material and oxygen-containing air, it is thus possible to form a combustion chamber in the lower zone of the roasting furnace in which the temperature exceeds the normal temperature in the remaining 25 parts of the roasting furnace, preferably maintained at 1100 to 1300 ° C. A particular advantage of this combustion chamber is that it has no requirements regarding said fuel. Neither the size of any lump fuel, the fuel consistency, nor the thermal value and residual fuel content.

Also, modification of an existing plant is feasible relatively simply, since it is only necessary to modify the bottom of the roasting furnace and the air supply system.

In order to control the temperature in the lowermost zone, it is necessary to provide the possibility of controlling the feed of the raw pulp, since the supply of large quantities of raw pulp lowers the temperature, due to the fact that calcination is an endothermic process.

In order to ensure a controlled supply of raw pulp to the bottom zone, it is necessary to ensure that the raw pulp introduced into the uppermost zone in the roasting furnace does not fall into the bottom zone.

Any such drop in the raw pulp can be appropriately prevented by providing a positive and relatively uniform velocity profile of the upwardly flowing air in the uppermost part of the lower zone of the roasting furnace.

There are numerous ways to ensure a positive velocity profile across the entire cross-section of the lowest 45 zone. A simple method is to ensure that the oxygen-containing gas flows into the lowermost zone in such a way that downstream currents do not occur in the cross-section.

In a particularly preferred embodiment of the invention in which the oxygen-containing gas is introduced and distributed in a suitable manner, the side (s) in the lower zone of the roasting furnace have (have) several smaller 50 orifices, all of which introduce hot oxygen-containing gas from the annular chamber. In this variant, it is only necessary for the chamber to be provided with a single hot gas supply point.

AND

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in further detail with reference to the drawing, wherein Fig. 1 shows a conventional cementing plant, Figs. 2 and 3 illustrate an embodiment of a roasting furnace in a device according to the invention. Fig. 5 shows the gas velocity profile in the combustion chamber 23 according to line II in Fig. 4.

DETAILED DESCRIPTION OF THE INVENTION

Figure 1 shows a generally known cement manufacturing plant. This device consists of a preheater 1 which consists of three preheating cyclones a, b and c, a roasting furnace 2 followed by a separately installed cyclone 3, and a furnace 4 followed by a cooler 5.

The feedstocks fall down through the apparatus upstream of the hot gas from the furnace 4 and from the cooler 5, which moves up through the roasting furnace 2 and the preheater L The feedstocks are then fed into the apparatus at the hottest end of the preheater 1 via line 6. gas to the preheating cyclone a, in which the material separates from the slurry and is directed through a downstream stream into an even more hot gas stream carrying the feedstock to the preheating cyclone b. In a similar manner, the feedstock is fed from cyclone b to cyclone c. the feedstock is separated in a cyclone and discharged via line 7 to an electrostatic precipitator and then discharged into a stack.

Once the feedstock has passed through the preheater 1, it is routed via line 8 to the roasting furnace 2, and the preheated feedstock is normally immediately introduced above the bottom into the roasting furnace.

The roasting furnace 2 in Figure 1 is of the SLC-type (Separate Line Calciner) and therefore only the oxygen-rich air from the cooler is passed through line 9. The ILC-type (In-Line Calciner) is charged with hot air from the furnace along with hot oxygen-containing air from the cooler. In conjunction with an SLC-type roasting furnace, the hot air from the furnace passes around the roasting furnace and passes directly to the preheater.

One or more of the burners 10 ensure that the temperature in the roasting furnace is raised to a level of approximately 850 to 950 ° C and, after the raw pulp has been calcined, is suspended through a separate cyclone 3 in which the calcined raw pulp is separated from the slurry and it is controlled via line 11 to the sintering furnace 4. The hot gas from the roasting furnace 2 rises to the outlet at the top of the separated cyclone 3 and is passed to the preheater L Finally, the calcined raw pulp passes through the furnace 4 in which the raw pulp is exposed . The result is the formation of a molten mass in which clinker minerals can form. The molten mass with clinker minerals clumps, and the finished clinker falls into the cooler where the clinker cools down to about 100 ° C.

Figures 2 and 3 show an embodiment of a roasting furnace 2 for a device according to the invention. Thus, in Figure 3, the roasting furnace 2 of Figure 2 is cut along line I.

The hot gas is fed to the roasting furnace 2 via two lines 21, which direct the hot gas horizontally to the roasting furnace 2 through two openings 20, one of which can be seen in Figure 3. under the guidance 8, a ski bridge 22 may be provided to prevent all raw debris from ending in the lower zone of the roasting furnace 2.

Effective distribution of the raw pulp across the cross-sectional area of the roasting furnace, either by unfolding the ski bridge or by using another distribution mechanism to ensure a suitable stopping of the raw pulp, also minimizes the pressure drop across this part of the roasting furnace.

In the lower part of the roasting furnace, a combustion chamber 23 is formed into which fuel is fed through the conduit 24 and the temperature in the combustion chamber 23 can be controlled by adding a smaller amount of raw pulp through the conduit 25. Fuel is supplied to the upper zone of the roasting furnace through one or more The fixed bottom means that the combustible material introduced through the conduit 24 is allowed to settle on the bottom, thereby creating a stationary fire. The bottom 27 may be configured such that any residual material can be removed, either by wiping or dripping the material through the bottom or by blowing it into the suspension. This embodiment is provided with holes 26 under the bottom 27 for extracting the remaining material.

Figure 4 illustrates another embodiment of a roasting furnace for an apparatus of the invention. In this embodiment, hot gas is introduced into the bottom zone of the roasting furnace 2 through a conduit 21 which, through a 20 annular chamber 28, distributes the hot gas through several openings 20 in the walls of the roasting furnace.

Figure 5 shows the velocity profile for the uppermost portion of the lowermost zone in a device similar to that shown in Figure 4 on line II according to which the hot oxygen-containing gas is introduced into the combustion chamber 23 through the annular chamber 28.

As can be seen from the figure, the velocity is positive, i.e. rising across the entire cross-sectional area. If the gas is rotated in the chamber, for example by tangentially introducing the gas, there is a risk that the velocity profile becomes negative for the central zone, i.e. with a downward velocity. >

Claims (6)

PATENT CLAIMS Cement clinker production apparatus comprising a preheater and a roasting furnace, in which the raw cement pulp is calcined at a temperature above 800 ° C and wherein the oxygen-containing fuel and gas are introduced into the lower zone of the roasting furnace, and a furnace in which the raw pulp burns and transforms into clinker, characterized in that the lower end of the roasting furnace (2) has a fixed bottom (27), 40 and that the oxygen-containing gas is fed to the downstream zone (23) in a horizontal direction, and that a less controlled amount of uncalcined raw pulp can be fed to the downstream zone (23) in the roasting furnace. Device according to claim 1, characterized in that the temperature in the lower zone (23) 45 in the roasting oven (2) is higher than the temperature in the upper zone of the roasting oven. Device according to claim 1 or 2, characterized in that the temperature in the lower zone (23) in the roasting oven (2) is higher than 1000 ° C. 50 Device according to claim 1 or 2, characterized in that the temperature in the lower zone of the roasting furnace (2) is maintained in the range of 1100 to 1300 ° C. -4GB 290901 B6 AND Apparatus according to claims 1 to 4, characterized in that the oxygen-containing gas is introduced into the lower zone (23) of the roasting furnace (2) through at least two openings (20) in the side (s) of the roasting furnace (2). Apparatus according to claims 1 to 5, characterized in that the oxygen-containing gas is introduced into the lower zone (23) of the roasting furnace (2) through at least two openings (20) in the side of the roasting furnace (2), arranged so as to maintain a positive velocity profile for the upward flow of gas at the top of the lowermost zone (23). Device according to claims 1 to 5, characterized in that the inner diameter of the upper part of the roasting furnace is 1.5 to 2 times greater than the inner diameter of the lower zone.